Systems that use the flow of a fluid, for example a liquid, to aid in the fabrication of a component, testing of a component, cooling of a component and the like are known. In addition, systems such as a stereolithography machine, ultrasonic testing probes and the like can exhibit decreased performance when gas bubbles are present in the liquid.
Stereolithography is an additive manufacturing process that incorporates a vat of liquid photopolymer resin and a light source such as a laser to build or fabricate parts, components, etc., one layer at a time. For each layer, the light source can trace a pattern of the part cross-section on the surface of the liquid resin and the exposure of the resin to the light solidifies the resin for that layer. Thereafter, a platform on which the part is located can descend into the vat of liquid by a single layer thickness and the light source can trace the pattern again and thereby solidify the next layer, the next layer also being adhered to the underlying and previously solidified layer. In some instances, a resin-filled blade can sweep across the part cross-section after the platform has descended into the vat by a single layer thickness and thus ensure that the part cross section is uniformly recoated with a fresh layer of the photopolymer resin.
The resin within the vat is typically pumped within a closed-cycle loop such that resin is removed from the vat, passes through a pump and is then re-introduced into the vat. The process of pumping the resin can introduce gas bubbles therewithin which are subsequently transferred into and present in the vat. If a bubble is present on the cross-section of the part when the light source traces the pattern, the bubble cross-section can be cured/hardened and result in a defect of the manufactured component. In addition, a cured/hardened bubble that is present on the top layer of the part can interfere with the resin-filled blade when it sweeps across the part cross section. As such, a bubble can result in the production of a faulty component and/or malfunction of the stereolighography machine such that the process of making the current part or component must be abandoned and the process restarted from the beginning.
Another concern with bubbles and the operation of a stereolithography machine is the fact that the viscosity of the liquid polymer can increase with time of operation and/or number of parts produced by the machine. In addition, as the viscosity increases, bubbles formed during the pumping process are harder to remove and replacement of the liquid is required. It is appreciated that frequent replacement of the liquid polymer can result in a significant increase of the overall cost associate with operating the machine.
With respect to ultrasonic testing, an ultrasonic probe can use water to provide a medium for ultrasonic waves to travel from a piezoelectric transducer to a component being tested. The water can also serve as the medium for the return of an echo wave from the component back to the transducer. In the event that a gas or air bubble is present in the liquid between the transducer and the component, erroneous readings can occur.
The problem with bubbles in such types of systems is known to those skilled in the art and efforts to reduce or eliminate such bubbles have been taken. For example, U.S. Patent Application Publication No. 2004/0159967 discloses a bubble elimination system for use with stereolighography machines in which ultrasonic transducers are used to vibrate the vat of the machine. The vibration is taught to cause bubbles within the vat to dislodge from a structure to which they are adhered to, float to the surface and eventually pop or be removed. However, such a system requires the use and addition of ultrasonic transducers, vibration of the vat tank, both of which can add to the cost, expense and complexity of the machine. As such, a cost-effective, relatively simple bubble reduction system for a fluid flowing system would be desirable.